Demonstration of a State-Insensitive, Compensated Nanofiber Trap

We report the experimental realization of an optical trap that localizes single Cs atoms ≃215nm from the surface of a dielectric nanofiber. By operating at magic wavelengths for pairs of counterpropagating red- and blue-detuned trapping beams, differential scalar light shifts are eliminated, and vector shifts are suppressed by ≈250. We thereby measure an absorption linewidth Γ/2π=5.7±0.1MHz for the Cs 6S_1/2, F=4→6P_3/2, F^'=5 transition, where Γ₀/2π=5.2MHz in free space. An optical depth d≃66 is observed, corresponding to an optical depth per atom d₁≃0.08. These advances provide an important capability for the implementation of functional quantum optical networks and precision atomic spectroscopy near dielectric surfaces.